Elastomeric film

ABSTRACT

An anti-slip film is produced by combining a thin, dimensionally stable plastic film having a smooth surface finish with a silicone elastomer having a low durometer and a textured and polished surface finish. The film may include adhesive means for adhering the film to objects, and label stock for displaying graphical and/or textual indicia.

This application is a continuation-in-part of U.S. application Ser. No.10/523,942, filed 8 Feb. 2005, titled “Silicone-Elastomer Film andMethod of Making Same.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to thin film silicone elastomers andmethods of manufacturing thin film silicone elastomers.

2. Description of Related Art

Most handheld electronic devices, such as cellular telephones,camcorders, cameras, computer-based digital cameras, CD and MP3 players,PDA's, remote controls, notebook computers, tablet PC's, video games,video game controllers, hair trimmers and shears, and a wide variety ofother handheld electronic devices, including carrying cases and pouchesfor these devices, have housings that are made of hard, smoothmaterials, such as plastic and metal. Although some of these devicesinclude hand grips and/or small rubberized components, they typically donot include any anti-slip material over a large portion of theirhousings. This is a problem, because when a user handles one of thesedevices, the slightest amount of mishandling can allow the device toslip out of the user's hand, which can lead to the device being droppedand damaged. In addition, when these devices are placed on a table orother surface, such as the dashboard of a vehicle, they are vulnerableto sliding or being knocked off onto the floor or ground, which can leadto breakage or permanent damage.

Most handheld electronic devices have housings that are made of hard,smooth plastic or metal. The front faces of these housings usuallyinclude ornamental shapes and designs, but the rear faces are typicallyplain and smooth. Often, the rear, side, and bottom surfaces includeswitches, buttons, and access ports for receiving interchangeablecomponents, batteries, and carrying cases. These switches, buttons, andaccess ports leave exposed joints, seams, and grooves. Flip-type andswivel telephones also include integral plastic and metal hinges andswivels.

In addition, many of these handheld electronic devices are configured tofit on top of other components or into accessory components, such ascaddies, cradles, chargers, docking stations, computer monitors,carrying cases, and clips. When coupled together, there is usually verylittle clearance between the device and the accessory component. As aresult, it is not possible to place a thick, anti-slip material directlyonto the device, as doing so would prevent or impede the device fromproperly mating with its accessory component.

In addition to adding anti-slip functionality to handheld electronicdevices, there are many other applications in which anti-slipfunctionality is desired. For example, in the printing industry, it isdesirable to have rollers and other paper handling components that havehigh gripping capacity and that are highly durable. There are countlessother material handling examples across many other industries in whichit is desirable to have durable, anti-slip functionality.

Also, many applications exist in the sport and recreation industries.For example, many sports require the use of handheld equipment, such asbats, rackets, paddles, sticks, and other devices with grippingsurfaces. In these sports, it is usually desirable to have anti-slipfunctionality associated with this equipment. In addition to handheldequipment, there are many sporting and recreation applications in whichit is desirable that there be anti-slip functionality between a usersclothing and his equipment.

Although there have been significant developments over the years in thearea of producing thin elastomers, considerable shortcomings remain.

SUMMARY OF THE INVENTION

There is a need for a thin film having a silicone elastomer coating foruse as an anti-slip skin, grip, or applique that can be applied tovarious items.

Therefore, it is an object of the present invention to provide a thinfilm having a silicone elastomer coating or layer applied to one surfaceof the film and a method for producing the film.

This object is achieved by providing a thin, dimensionally stable,smooth plastic film, disposing a silicone elastomer onto the plasticfilm, and imparting a polished surface finish to the silicone elastomer.In the preferred embodiment, the polished surface finish is imparted tothe silicone elastomer by a casting means, such as a casting film, theplastic film-silicone elastomer assembly is cured, and the casting meansis removed.

The present invention provides significant advantages, including: (1)stability of the elastomer as related to processing and use is provided;(2) a stabilized bonding surface for applying to other materials isprovided; and (3) the ability to efficiently handle a very thinelastomeric coating having a very low durometer is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, includingits features and advantages, reference is now made to the detaileddescription of the invention taken in conjunction with the accompanyingdrawings in which like numerals identify like parts, and in which:

FIG. 1 is a perspective view of a film of the present invention;

FIG. 2 is a side view of a film according to the invention;

FIG. 3 is an enlarged view of a section of the film of FIG. 1, thesurface texture being visible;

FIG. 4 is a side view of a second embodiment of the film of the presentinvention, the film having an adhesive layer added;

FIG. 5 is a side view of a third embodiment of the film of the presentinvention, the film having adhesive layers and a label stock added;

FIG. 6 is a side view schematically illustrating the method used tomanufacture the film of FIG. 1;

FIG. 7 is a perspective view of a handheld electronic device, the devicehaving films of the present invention applied to outer surfaces of thedevice for use as anti-slip skins;

FIG. 8 is a front view of a ping-pong paddle having a film of thepresent invention applied to the striking surface of the paddle; and

FIG. 9 is a front view of a hand having films of the present inventionapplied to the fingertips for use as anti-sip skins.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the making and using of various embodiments of the presentinvention are discussed in detail below, it will be appreciated that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of exemplary waysto make and use the invention, and do not limit the scope of theinvention. It should be noted that the layers in the figures are notdrawn to scale.

The present invention is directed to a thin, soft, silicone elastomerfilm for use as an anti-slip skin, or applique. The skin can be applied,adhered, sewn, or otherwise attached to objects, a person's skin, theclothing of a user, or placed between objects, all of which act toprevent or reduce undesired relative motion between adjacent objects.

According to the present invention, a silicone elastomer is bonded to athin, dimensionally stable plastic film substrate to form a flexible,thin film, referred to herein as a “silicone-elastomer film.” It hasbeen found that the use of a silicone material having a low-durometer,i.e., less than 40 on the Shore A scale, and a dimensionally stable,smooth, plastic film having a surface energy of about 40 Dynes/cm,provides the best results. It will be appreciated that many thin plasticfilms are not dimensionally stable. This configuration overcomes many ofthe problems associated with thin elastomeric sheets. For example, withthe silicone-elastomer film of the present invention, the siliconeelastomer is stabilized and prevented from “stretching” and sliding offthe surface to which it is applied. In addition, an inexpensive acrylicpressure sensitive adhesive may be used to bond the silicone-elastomerfilm to other surfaces.

The silicone-elastomer film is durable, resilient, and capable ofadhering to a suitable acrylic pressure sensitive adhesive. In thepreferred embodiment of the present invention, the silicone elastomer isapplied to the plastic film. Then, a textured and polished surfacefinish is imparted to the silicone elastomer by a casting means having apolished surface finish. This process creates a textured and polishedsurface finish on the silicone elastomer. The phrase “surface finish”will be used herein to describe the surface of materials on a very fine,or microscopic, scale; whereas the phrase “surface texture” will be usedto describe the surface of materials on a larger scale, i.e., toindicate the presence of raised bumps, dimples, or ridges that can beseen with the naked eye and felt by hand.

The production of a silicone elastomer with a polished and texturedsurface finish represents a significant discovery in the presentinvention. It has been found that the use of such a silicone elastomergreatly improves the performance characteristics of thesilicone-elastomer film. An equally important discovery in the presentinvention is the production and use of the thin, dimensionally stable,smooth plastic film substrate. These discoveries provide significantbenefits, including: (1) the casting means releases cleanly from thesilicone elastomer after curing; (2) the silicone elastomer issignificantly more “grippy,” i.e., has a higher coefficient of frictionwith more anti-slip functionality; and (3) the silicone elastomer isresistant to collecting dust and debris.

Referring to FIGS. 1 through 3 in the drawings, the preferred embodimentof a silicone-elastomer film 11 according to the present invention isillustrated. As shown in FIG. 1, film 11 is formed as a sheet, and maybe formed as a continuous sheet on a roll (not shown). FIG. 2 is a sideview of film 11 showing a two-layer construction of film 11, in which alayer of silicone elastomer 13 having an exposed surface 19 with apolished surface finish is disposed on an upper surface 17 of a thinplastic film substrate 15. FIG. 3 is an enlarged view showing thepattern of the surface texture shown in FIGS. 1 and 2, with upraisedbubble-shaped dimples 21 being separated by narrow valleys 23.

As explained above, the textured and polished surface finish ofsilicone-elastomer film 11 is preferably formed by a casting means, suchas a casting film, having a polished surface finish. It will beappreciated that the surface finish of surface 19 of silicone elastomer13 may also be formed by other means, such as tools, dies, or rollers;provided that such means imparts, imprints, or transfers, the desiredtextured and polished surface finish to silicone elastomer 13. Surface19 is preferably formed to have a surface texture or pattern, as shown,although surface 19 may alternatively be matte or smooth. It has beenfound that, in some instances, the surface texture of surface 19 doesnot contribute significantly to the anti-slip functionality of film 11;however, certain surface textures do hide imperfections in film 11 andprevent dust and debris, which are easily seen on matte and smoothsurfaces, from collecting on surface 19. This improves the look and feelof silicone-elastomer film 11.

Plastic film substrate 15 is a thin, flexible film, preferably a clearfilm about 0.002 inches thick, that forms and provides a flexible,durable, dimensionally stable substrate. It is preferred that plasticfilm 15 have a smooth surface finish, as may be attained with aco-extrusion process, and have a surface energy lower than about 40Dynes/cm. This combination ensures a strong bond between plastic film 15and silicone elastomer 13. This unique bond prevents silicone elastomer13 from easily being detached from plastic film 15 during manufactureand use of film 11. For aesthetic purposes, plastic film 15 and/orsilicone elastomer 13 may be tinted or may include embedded or printedgraphical indicia. It is preferred that the combined thickness ofsilicone-elastomer film 11 be no greater than about 0.032 inches.

Silicone elastomer 13 is formed to have a low-durometer, i.e., less than40 on the Shore A scale. This, along with the inherent bondingcharacteristics of silicone materials, facilitates bonding with plasticfilm 15. Silicone 13 may be applied to plastic film 15 by pouring,spraying, spreading, doping, or any other conventional application meanssuitable for applying a silicone material to solid sheets or films.However, as described below, the preferred method of applying siliconeelastomer 13 to plastic film 15 is by controlled pouring in a continuousproduction process in which silicone elastomer 13 is sandwiched betweenplastic film 15 and a casting means having a textured and polishedsurface finish.

Referring now to FIG. 4 in the drawings, an alternative embodiment ofthe film of the present invention is illustrated. In this embodiment, afilm 25 has an upper portion 26 that has the same construction as film11 described above, in that a silicone elastomer 27 is applied onto anupper surface 29 of plastic film 31. As such, silicone elastomer 27 hasan exposed surface 33 with a textured and polished surface finish. Toprovide a means of affixing film 25 to an object, a layer of adhesive 35is applied to a lower surface 37 of plastic film 31, and a release liner39 is placed against surface 41 of adhesive 35 for preventingcontamination or setting of adhesive 35 prior to installation of film25. Plastic film 31 provides a suitable base for which to bond adhesivelayer 35, as it has been found that it is difficult to obtain a durablebond directly between adhesives and cured silicone materials. Adhesive35 may be applied as a tape by other appropriate means, such as inliquid form. Prior to use, release liner 39 is removed from adhesive 35,allowing film 25 to be adhered to a surface.

Referring now to FIG. 5 in the drawings, a second alternative embodimentof the film of the present invention is illustrated. In this embodiment,a film 43 has an upper portion 44 that has the same construction as film11 described above, in that a silicone elastomer 45 is applied onto anupper surface 47 of a plastic film 49. As such, silicone elastomer 45has an exposed surface 50 with a textured and polished surface finish. Alabel stock 51, which may include graphical and/or textual indicia orother desired items, is adhered to a lower surface 53 of plastic film 49by applying an adhesive layer 55 to an upper surface 54 of label stock51. This allows any graphical indicia on label stock 51 to be visiblethrough silicone elastomer 45 and plastic film 49. To allow forapplication of film 43 to a surface, a second adhesive layer 57 isapplied to a lower surface 58 of label stock 51, and a release liner 59is applied onto a lower surface 61 of adhesive layer 57.

Referring now to FIG. 6 in the drawings, the preferred method ofmanufacturing a silicone-elastomer film 91 according to the presentinvention is schematically illustrated. The first step in the process isto form or provide a casting means, such as a casting film 71, that isadapted to transfer a textured and polished surface finish to thesilicone elastomer. Casting film 71 may be formed by a wide variety ofconventional means for forming such films. The production of castingfilm 71 may be an integral part of the process of manufacturingsilicone-elastomer film 11, or casting film 71 may be produced in aseparate process prior to use in an off-site facility and stored insheets or rolls 65. This allows casting film 71 to endure the heat ofthe curing process described below without undergoing any undesirablechanges in shape, dimensions, or composition.

Casting film 71 is conveyed toward one or more nipping, or pinch,rollers 81, 83. At the same time, a plastic film substrate 73, which ispreferably stored in a roll 75, is also conveyed toward nipping rollers81, 83. Due to the thinness of plastic film 73, it is preferred thatplastic film 73 be heat stabilized prior to use. This heat stabilizationensures that plastic film 73 can endure the heat cycle of the curingprocess without cockling or buckling. This prior heat stabilization ofplastic film 73 is not typical of plastic films.

Before casting film 71 and plastic film 73 are drawn through nippingrollers 81, 83, a volume of silicone elastomer 79 is disposed on theupper surface of plastic film 73, preferably in liquid form by a nozzle77, or a similar device. Then, plastic substrate 73, casting film 71,and silicone elastomer 79 are drawn between nipping rollers 81, 83. Thiscauses silicone elastomer 79 to spread evenly at a selected thicknessover plastic film 73 and transfers the textured and polished surfacefinish of casting film 71 to the exposed surface of silicone elastomer79. This nipping process forms a film assembly 85 that is then subjectedto a curing process, which is indicated by area 87 in the FIG. 6. Curingprocess 87 may include raised temperatures and pressures for varyingdurations of time. The specific temperatures, pressures, and cure timesmay vary depending upon the specific characteristics that are desired inthe final film. It will be appreciated that other layers of materials,such as adhesives, label stocks, and release liners, may also becombined with film assembly 85, and that these other layers may be addedbefore or after curing process 87.

Next, casting film 71 is removed from film assembly 85 and captured onroller 89, leaving a completed silicone-elastomer film 91 having atextured and polished surface finish according to the present invention.Once manufactured in sheet form, silicone-elastomer film 91 may beconfigured for a wide variety of uses and applications, by cutting,shaping, and other post-processing steps.

In an alternative method of manufacture, casting film 71 is reused afterit is removed from film assembly 85. This embodiment is represented bythe phantom lines in FIG. 6. In this embodiment, a film return loop 99is provided so that casting film 71 may be returned to a location in theprocess prior to passage through nipping rollers 81, 83.

The production method shown in the figures and described above is onlyone example of a configuration for manufacturing the silicone-elastomerfilms 91 according to the present invention. The feed paths of castingfilm 71 and plastic film 73 may be configured in a variety of ways toachieve the same results. For example, the positions of the feed pathsof casting film 71 and plastic film 73 may be reversed, with siliconeelastomer 79 being applied to casting film 71, rather than plastic film73, prior to nipping rollers 81, 83. Another possible configuration hasthe feed paths of casting film 71 and plastic film 73 in generallyvertical orientations.

Referring now to FIGS. 7 through 9 in the drawings, some possible usesof the silicone-elastomer film of the present invention will now bedescribed with respect to the configuration of FIG. 4. Becausesilicone-elastomer film 25 is typically formed as a sheet, a user maycut or otherwise shape portions of the sheet to create desired shapesand sizes of film 25. The user then removes release liner 39 fromadhesive 35, and applies each film 25 to a selected surface. Film 25then acts as an anti-slip applique for preventing or reducing movementof the selected surface relative to an adjacent surface.

In FIG. 7, a handheld electronic device 101, in this instance a mobiletelephone, onto which silicone-elastomer films 103, 105 are adhesivelyaffixed for use as anti-slip skins, is shown. Skin 103 is applied to anouter surface 107 of device 101, and skin 105 is applied to outersurfaces 109, 111. The outer surface of each skin 103, 105 is preferablyformed to have a bubble pattern texture and polished surface finish, asshown in FIG. 3 and described above. Skins 103, 105 provide anti-slipfunctionality when device 101 is placed against other objects orsurfaces because the exposed silicone material of skins 103, 105 gripsthe adjacent surfaces.

In FIG. 8, a silicone-elastomer film 113 according to the presentinvention is shown applied to the striking surface 115 of a ping-pongpaddle 117. Silicone-Specification elastomer film 113 ensures a goodlateral grip between paddle 117 and a ball (not shown) struck by thepaddle, thereby enhancing the ability of the user to impart spin on theball when striking the ball. It will be appreciated that thesilicone-elastomer films of the present invention may be used on a widevariety of sporting equipment and in a wide variety of recreationalapplications.

In FIG. 9, a silicone-elastomer film 119 is shown in another use. Film119 has been configured into small shapes for application to a user'sfingertips 121. This provides for high levels of grip between fingertips121 and objects being manipulated by the user. For example, films 119may be used to allow the user to more easily pull sheets of paper from astack, or to count money. An advantage of using films 119 in thisapplication is that fingertips 121 are not fully enclosed, as withthimble-type fingertip appliances. This allows the user's fingers to“breathe,” and prevents the user from feeling discomfort from heatbuildup around fingertips 121.

The potential applications of the present invention go far beyond theuses mentioned above. The silicone-elastomer film according to thepresent invention may be used in many different applications across awide variety of industries, particularly when configured, cut, shaped,and formed for specific applications. For example, the present inventionmay also be used as follows: (1) as an outer surface of a sleeve for aprinter roller or other paper handling equipment; (2) as a self adhesive“hand pad” for weight lifters; (3) as a grip for flashlights; (4) aspads for eyeglass nosepieces; (5) as strips to be applied to the bottomof tool trays to keep tools from sliding; (6) as “barefoot” footwear;and (7) as an anti-slip skin for medical devices.

In other applications, the film according to the present invention canbe used as an applique for, or sewn into, uniforms, clothing, or gear.For example, in motocross, when riders grip their handlebars for longperiods of time, their hands and arms become fatigued. The film of thepresent invention may be placed on the riders pants to allow the riderto periodically grip the motorcycle with his legs. This helps relievethe fatigue in the rider's hands and arms. It will be appreciated thatthe present invention has additional applications in the motocrossindustry.

In an alternate embodiment, the silicone elastomer is disposed on bothsides of the plastic film. This can be done, for example, by eithercoating both sides of the plastic film, or by adhering twosilicone-elastomer films together back to back. This configurationallows for anti-slip functionality on both sides of thesilicone-elastomer film, and allows the use of the present invention inapplications in which it is undesirable to adhere the silicone-elastomerfilm directly to an object.

In another alternate embodiment, substrate 15 and release liners 39 and59 of films 11, 25, and 43, respectively are configured or treated toallow films 11, 25, and 43 to be more easily manufactured and stored inrolls. In this embodiment, substrate 15 and release liners 39 and 59 areconfigured or coated, treated, or otherwise prepared to quickly andeasily release from the exposed elastomeric surfaces when films 11, 25,and 43 are rolled up. The configuration or treatment of substrate 15 andrelease liners 39 and 59 ensures that the adjacent layers of films 11,25, and 43 that are formed by capturing films 11, 25, and 43 into rollsdo not stick together. There are significant advantages to treating bothsides of substrate 15 and release liners 39 and 59, or by makingsubstrate 15 and release liners 39 and 59 out of selected releasablematerials, including: (1) the shelf life of films 11, 25, and 43 can begreatly extended; (2) additional dimensional stability is added; (3)waste is greatly reduced; (4) films 11, 25, and 43 can be captured onrolls faster and easier; (5) wrinkling and cockling is prevented.

The present invention may be used in wide variety of applications. Thefilms of the present invention may be used to protect the windshields,windows, mirrors, and other breakable or scratchable parts on vehiclesin storage or transport, including automobiles, motorcycles, boats, andaircraft, to name few. In such applications, the silicone elastomersurface clings to the surface to which it is applied and the substratematerial protects the surface from scratching and other damage. Thesilicone elastomer material can be quickly and easily removed, and doesnot leave any residue on the surface when removed.

In another application, a sheet of silicone elastomer film is placedover a keyboard-type touchpad to provide anti-slip functionality andtactile feedback to the user. This embodiment can be used to replace theLEXAN sheets that are currently placed over flat touchpads. For example,the silicone elastomer material is applied to a label stock and thelabel stock is then applied to a membrane-type switch to provide tactilefeed back. It will be appreciated that the silicone elastomer materialcan have a selected surface finish that allows the user to tactilelyidentify certain keys and locations on the touchpad. In addition, thefilm may include raised portions over the switches to allow a snap-typefeedback. In another version of this embodiment, small individual piecesof the silicone elastomer film are placed on the tops of individual keysof keyboards to provide anti-slip functionality to the user.

In yet another application, the film of the present invention may beused as a fastening device. In this embodiment, a silicone elastomerfastening film is adhered to a first device, and an adhesive backedplastic film is adhered to a second device. When the silicone fasteningfilm is brought into contact with the plastic film, the soft siliconeelastomer material wets out on the plastic film causing the seconddevice to remain quasi-fastened to the first device. This embodiment ofthe present invention is particularly well suited for applications inwhich sun and heat are factors, such as securing devices to a cardashboard, for example, storing a tire pressure gauge on the dashboardof an automobile.

In another application, the silicone elastomer film of the presentinvention may be used as a mouse pad. In this application, a small sheetof film is placed face-down on a surface. The exposed silicone elastomermaterial prevents the sheet from moving relative to the surface, butallows quick and easy removal without leaving an adhesive residue.Because the plastic substrate is very smooth with a very low coefficientof friction, a highly lubricious mousing surface is formed. A user canthen move a mouse or other pointing device over the plastic surface withlittle or no drag or resistance. However, the texture of the siliconeelastomer does transfer through the plastic film providing a desirablesmooth texture. This embodiment is ideal for precision pointing devices.

It is apparent that an invention with significant advantages has beendescribed and illustrated. Although the present invention is shown in alimited number of forms, it is not limited to just those forms, but isamenable to various changes and modifications without departing from thespirit thereof.

I claim:
 1. An anti-slip film for a cellular phone having at least onehard, smooth exterior surface with a low coefficient of friction, theanti-slip film comprising: a clear dimensionally stable, thin plasticfilm having: a surface energy of about 40 Dynes/cm; an upper surface;and a lower surface; a thin layer of clear non-stretchable siliconeelastomer adhesively bonded to the upper surface of the thin plasticfilm, the thin layer of silicone elastomer being adapted to retain adimensionally stable shape, the layer of silicone elastomer having: adurometer of less than 40 on the shore A scale, and an exposed topsurface with a casted textured and polished surface finish the exposedtop surface creating a high coefficient of friction relative to a hardsurface which the cellular phone is placed thereupon so as to preventslipping; a first adhesive layer bonded to the lower surface of theplastic film; and a separate layer of label stock having: an uppersurface bonded to the first adhesive layer and being configured todisplay a graphical indicia visible through both the clear plastic filmand the clear silicone elastomer; and a lower surface; a second adhesivelayer applied to the lower surface of the label stock; and a releaseliner removably attached to the second adhesive layer; wherein therelease liner is removed and the second adhesive layer is bonded to theexterior surface of the cellular phone.